A memory device having a three-dimensional structure has been proposed. The memory device includes a stacked body in which a plurality of electrode layers that function as control gates of memory cells are stacked with insulating layers interposed between the electrode layers. Memory holes are made in the stacked body, and silicon bodies used to form channels are provided on the side surfaces of the memory holes with a charge storage film interposed between the silicon bodies and the side surfaces of the memory holes.
The memory hole is made by, for example, reactive ion etching (RIE). As the aspect ratio of the memory hole increases, the lower side surface of the memory hole made by RIE becomes tapered; and there is a tendency for the diameter to decrease toward the lower portion of the memory hole. The fluctuation of the diameter in the depth direction of the memory hole may cause fluctuation of the device characteristics between the upper layer side and the lower layer side.